If you do not have an ophthalmologist, or if you are away from home, find a teaching hospital that has a training program in ophthalmology, go to their emergency room, and ask to see the eye resident on call. This chapter describes several examples of each type of eye problem.
During transcription, enzymes called RNA polymerases build RNA molecules that are complementary to a portion of one strand of the DNA double helix (Figure 3). Figure 3: RNA polymerase at work. RNA polymerase (green) synthesizes a strand of RNA that is complementary to the DNA template strand below it.
Starting with DNA, the process of transcription makes RNA molecules, including a type that carries the information encoded in DNA. The word transcribe means to write something down in the same language; for example, you transcribe when you take notes at a lecture.